It is well known to connect coaxial cables, hosepipes, and other conduits for material or data end-to-end by providing a connector member with an external screw thread on one conduit end, and an internally threaded nut rotatable but captive on a connector body at the other conduit end.
It is well known that connectors used on satellites, military aircraft, and missile systems experience several Gs of shock and high amplitudes of vibration, which can cause the nuts to loosen, which degrades signal performance. The risk of loosening in use can be reduced by screwing up the nut very tightly. However, the externally threaded member may be a post mounted on an external panel of a device to which the cable is to be attached. Such posts are typically mounted by screwing the threaded post into a threaded hole in the panel, or by passing the threaded post through a hole in the panel and screwing a retaining nut onto it. The tighter the nut is screwed onto the post, the more likely it is that the post will turn and loosen its own mounting. As a result, even during system assembly, companies can incur major repair costs, because it becomes necessary to pull the subsystems out to re-tighten loosened nuts and posts.
Connector designs have previously been proposed, manufactured and used to assure that their mating parts will be locked together and cannot be accidentally loosened as a result of shock or vibration. These design approaches include such techniques as lock wire nuts, secondary nuts, cotter pins, lock washers, spring loaded locking mechanisms, etc. Although such techniques have proven to be effective in some applications, they involve additional, costly assembly operations and/or additional parts. They may also be difficult to install in crowded locations that may not be easily accessible.
Additionally, some previously proposed designs are not real “true locking” designs, because the nut is locked only to the rear of its own connector body rather than to the mating connector member. In these designs, the connection can loosen if the connector body as a whole rotates relative to the connector member.
FIG. 1 illustrates an example of a previously proposed connector assembly 100, in which a nut 102 with wire holes 104 locks to the mating connector member 106, which has wire holes 108. This is an example of a “true” locking design. A wire 110 passes through the holes 104, 108 in the first and second connectors 102, 106, effectively “locking” them together. The ends of the wire are twisted together at 112. Although this can provide an effective locking mechanism it has several disadvantages. It is time consuming, expensive, and difficult to achieve on crowed system platforms. Also, it is not “cyclical.” That is, it cannot be repeatedly attached and released without the destruction and replacement of the wire 110.
FIG. 2 illustrates an alternative previously proposed self-locking connector 120. In this design, the nut 122 has a ramped feature 124 with a spring loaded sleeve 126 that locks the connector from the rear of the body. The spring 128 locks the sleeve to the nut 122 when not retracted, and has a channel 130 that accommodates a locking pin 132. When the sleeve is retracted (to the right in FIG. 2) and turned by a quarter turn, the sleeve 126 is disengaged from the nut 122 and held in the unlocked position. Although fast and easy to use, a disadvantage of this design is that it does not lock the nut 122 to the mating connector or panel 134. If either of the connector halves 134, 136 rotates relative to the other, the nut 122 can loosen or even break free and loss of the electrical signal or environmental seal results.
Referring to FIG. 3, U.S. Pat. No. 5,186,501 to Mano proposes a connector device 140 that has a series of ramps 142 on the distal face of the nut 144 with matching ramps 146 on the adjacent face of an opposing Belleville spring washer 148 that bears against a shoulder 150 of the mating connector member 152. In this case the spring 148 provides a compressive resistive force when the nut 144 is threaded into place, effectively locking the nut 144 to the connector member 152. One disadvantage of this design is that it requires a known spacing between the toothed face 142 of the nut 144 and the shoulder 150 to function correctly. That dimension is effectively determined by the length of the externally screw threaded portion 154 of the connector member 152 from the shoulder 150 to the front end 156 where it mates with the connector body 158 on which the nut 144 is captive. Mano's device is therefore not suitable for use with connector members 152 supplied by unknown third party vendors, where the length of the screw threaded portion 154 cannot be controlled.
In addition, in a panel-mounted configuration, the mounting panel 160 typically overlies the shoulder surface 150 shown in FIG. 3, and the washer 148 bears on the front face of the panel 160, or on a retaining nut (see nut 55 in FIG. 4) screwed against the front face of the panel, and the thickness of the panel usually cannot be controlled. Mano's device is therefore not suitable for use with many panel mounted connectors. Another disadvantage of this design is that it relies on friction at the surfaces where the Belleville washer 146 rests on the shoulder 150, and may not function reliably when lubricants are present on those surfaces. However, if the friction is sufficiently high completely to prevent rotation, the nut 144 cannot be released, so the device becomes non-cyclical.
There is a continuing need for a simple, cyclically re-useable, self-locking connector to interconnect the mating ends of connector bodies, especially in the space, military and aerospace industries, and especially to hold coaxial cables coupled together in a fluid sealed manner and more stringently for continuous radio frequency operation while in the presence of shock and vibration.